Magnetic switch device



July 11, 1939. w $M|TH 2,165,514

MAGNETIC SWITCH DEVICE Filed Feb. 19, 1937 z'sheets-"sheet 1 INVENTOR BY WARD L. JM/TH 'rgORNEY 11, 1939- w. L. SMITH 2,165,514

MAGNETIC SWITCH DEVICE Filed Feb. 19, 1957 2 Sheets-Sheet 2 ATTORNEY Patented July 11, 1939 UNITED STATES PATENT OFFICE MAGNETIC SWITCH DEVICE Application February 19, 1937, Serial No. 126,674

10 Claims.

This invention relates to an electro-magnetically operated switch device and particularly to that type of switch device which is held in closed position by a main spring or similar means and which is opened and retained in open position against the force of the main spring by electro-magnetic means during energization of the latter.

One of the many uses of such devices is in the control of the dynamic braking circuit of electric motors wherein, upon energization of the motor, a coil of the switch device is energized to open the contacts and remove the braking resistance from the circuit, and upon failure of the power or deenergization of the motor for any reason, the coil of the device is deenergized and the contacts are closed by the main spring so as to reconnect the dynamic braking resistance across the motor armature. The contact is usually provided through a stationary contact and a movable contact, the latter being carried on an armature which is moved to contact making position by the main spring and to contact breaking position i by the electro-magnetic means.

Efiicient operation of such devices requires the maintenance of adequate and uniform contact pressure between the contacts. To provide such contact pressure, the movable contact is usually attached to an auxiliary arm pivoted on the armature, and is urged toward the contact making position by an auxiliary spring which cooperates with the contact and the armature. When the contacts touch, the auxiliary spring is compressed so as to maintain a predetermined uniform pressure when the armature has reached the limit of its travel. This same arrangement also effects a wiping or rolling action between the contacts, causing them to close first at the tips and then to slide or roll relatively across each other, thus removing dirt and oxides and concentrating at the tips any are which might occur upon closing.

The contacts of many commercial types of spring closed switches are destroyed more quickly than are those of the magnetically closed switches of corresponding design and capacity, the principal reason for this being that in the operation of conventional spring closed contacts, a momentary delay occurs during the period of opening the contacts. This delay is occasioned by the sudden changes in the relative amounts of spring pressure and magnetic pull prior to the time when the operating coil has reached full strength. This short delay permits the contacts either to touch each other under low pressure with resulting increased resistance at the point of contact and consequent deleterious heating or to pause so nearly together in the opening movement that arcs form thereacross.

One of the principal objects of the present invention is to provide a spring closed electro-mag- 5 netic switch device in which the contacts open without excess heating or arcing.

A correlative object is to provide a spring closed electro-magnetic switch in which the contacts open and substantially instantaneously assume a sufliciently spaced relation to eliminate appreciable arcing.

Another object is to provide a means whereby the movable contact is held in tight engagement with the cooperating stationary contact until the electro-magnetic means is sufficiently energized to assure the instantaneous action required.

A more specific object is to provide an auxiliary magnetic circuit cooperating with the armature for holding the contacts in firm contact relation 20 until the main operating magnetic circuit has built up to point to provide a pull which will separate the contacts with a uniform and rapid motion.

Another specific object is to provide a means 25 whereby the movable contact of a spring closed switch device which has an auxiliary spring arrangement for permitting wiping or rolling action of the contacts may be opened with a uniform movement, and which means is readily adapted 30 for use with conventional switch devices of this character.

Other objects and advantages will become apparent from the following specification wherein reference is made to the drawings in which: 35

Fig. 1 is a side elevation of the invention as applied to a switch device or contactor of commercial design;

Fig. 2 is a wiring diagram of one system of coil connections which may be used in the present invention; and

Figs. 3 and 4 are respectively combined wiring and magnetic circuit diagrams of modifications of the present invention.

Referring first to Fig. l, the invention is illustrated in connection with a commercial switch device, which comprises the usual insulating base I on which is mounted a suitable support 2. A stationary contact 3 is mounted on the support 2 and is connected through a blow-out coil 4 with a terminal 5 secured to the base i. A movable contact 6 is provided and is carried on an auxiliary rocker arm 1 which is pivotally supported on an armature B by means of a pivot 9. The arm 1 is preferably conducting material. A flexible connector I8 is connected to the arm I and to a terminal II mounted in the base I, thus providing a circuit from the terminal 5 to the terminal II through the contacts 3 and 6 when the contacts are closed. Uniform contact pressure and wiping action of the contacts 3 and 6 are eifected by the relative movement provided between the auxiliary rocker arm I and the armature 8. The arm I is urged toward contact making position about its pivot 9 by a suitable auxiliary spring I2 which is interposed between the arm I and a stop I3 on the pin M, the pin I4 being fixedly secured to the armature 8. If desired, however, the stationary contact may be operated by a spring such as spring I2 and the movable contact fixedly mounted on the armature 8. The armature 8 is pivoted on a knife edge fulcrum I5 on a supporting bracket I6 which, in turn, is mounted on the base I. Due to the force exerted by the auxiliary spring I2 on the arm I when the contact 6 is in engagement with the contact 3, the reaction is such as to urge the armature to rotate in a clockwise direction about the fulcrum I5.

The supporting bracket I6 is magnetic material and forms a continuation of an iron core piece H of a main contact opening coil I9. The armature 8 preferably is provided with an insert I8 of magnetic material, although other types of armatures may be employed. The coil I9 is such that when energized it operates to rotate the armature 8 in a clockwise direction about the fulcrum I5 to a position for breaking contact between the contacts 3 and 6. The armature 8 is held in position for making contact between the contacts 3 and 6 by means of a suitable main spring 28 which is operatively interposed between a stationary bracket 2I on the bracket I6 and a connecting rod 22 connected to the armature 8. The spring 28, therefore, operates to rotate the armature about the fulcrum I5 in a counter-clockwise direction into the contact making position.

In the structure thus far described it is apparent that when the coil I9 is energized for moving the armature in a clockwise direction about the fulcrum I5 to break contact and open the circuit, it must overcome the resistance of the main spring 28. Since the spring l2 also tends to rotate the armature in a clockwise direction its effect and that of the coil I9 are cumulative in overcoming the spring 28. It is apparent, however, that upon limited movement of the armature in a clockwise direction the spring I2 is relieved and is no longer eifective in assisting the coil I9.

At the time of initial energization of the coil l9, there is a slight pull on the armature through the medium of the magnetic circuit provided by the insert I8, the bracket I6 and the core piece IT. This pull, together with the assistance of the spring I2, tends to separate the contacts 3 and 6, or at least reduce the pressure of contact therebetween. This action occurs before the coil I9 has built up to full strength and may be such as to relieve the auxiliary spring I2. Thus, it is brought about that the assistance of the spring I2 is removed before the coil I9 is sufficiently strong to overcome the resistance of the spring 28 unassisted.

Due to the difference in lengths of the effective lever arms of the springs I2 and 28 with respect to the fulcrum I5, when the contacts are in closed position, the moment of the auxiliary spring I2 on the armature 8 for rotating it about the fulcrum I5 is nearly equal and opposite to that of the main spring 28. For this reason, the very small initial pull exerted by the operating coil I9 when it is initially energized and before it is up to strength starts the movement of the contacts 3 and 6 to open position and will continue this movement until the spring I2 is no longer effective. Thereupon the contacts will be stopped or slowed down in their movement toward open position while under light contact pressure or very slightly separated. This rather slow or irregular opening and light contact pressure result in heating and sparking. If, however, the movement of the armature by the coil I9 is prevented until the coil I9 is up to operating strength, the effect of the spring I2 is relatively unimportant and ineffective. It is desirable therefore to provide means for assisting or augmenting the holding force provided by the spring 28 so that the coil I9 must be up to strength before it can initiate any movement of the armature. Likewise it is desirable that the augmenting force be reduced rapidly after the movement has been initiated by the coil I9 reaching full or predetermined strength so that a steadier pull results. In order to obtain the time delay necessary to permit the coil I9 to build up to strength before it initiates any movement of the armature 8, a core piece 38 is provided and is mounted on the base I in a position to serve also as a closing limit stop for the armature. The core piece 38 is of magnetic material and a correspondingly magnetically responsive insert 3| is mounted on the armature 8 in position to engage the core piece 38 when the armature B is in contact making position.

A coil 32 is mounted on the core piece 38 and is of sufficient strength when energized so that its force, added to that of the spring 28, prevents movement of the armature 8 by the coil I9 until the coil i9 has reached a comparatively high value of excitation. The magnetic coil 32 is of relatively low inductance since the core 38 forms the only iron portion of the flux path. Since its strength need not be as great as that of the coil IS, the coil 32 has much less inductance than I the coil I9 and its attractive strength builds up much more rapidly and while the coil I9 is only initially or partially energized. Thus, there is no movement of the armature by the coil I9 u'pon initial excitation of the coil I9. When the coil has reached the desired degree of excitation and strength to overcome both the resistance or pull of the magnetic circuit through the core piece 38 and insert 3! and the spring 28, it is of a strength much beyond that necessary to overcome the full strength of the spring 28 alone. Furthermore, at the instant that the armature 8 has been moved the slightest amount by the coil I9, the resistance to movement provided by the core 38 and insert 3! drops off very rapidly due to the resultant increase in the air gap and does not offer appreciable resistance to movement by the coil I9. Therefore, by the time the force of the spring I2 no longer assists the coil I9 in moving the armature and in overcoming the spring 28, the coil I9 is so highly excited that it readily overcomes the spring 28 unassisted and moves the armature steadily and rapidly to contact breaking position.

As better illustrated in Fig. 2, the auxiliary coil 32 preferably is connected in parallel with the coil I8 through the conductors 33 and 34 but it may be connected in series with the coil I9 or in series with the main power circuit, or it may 75 be separately excited. The coil 32 is preferably deenergized by the separation from auxiliary contacts 35 and 36 of the bridge connector 31. The bridge 3'! may be mechanically connected to the armature in a suitable manner, as illustrated in Fig. l, for breaking contact when the armature 8 is moved in the direction for opening the contacts 3 and, v6 and for making contact upon return movement of the armature. When a circuit to the coil I9 is interrupted, the flux set up by the coil will die out rapidly since there is no completed shunt circuit to cause delayed action, the circuit having been opened by movement of the connector 31.

Referring next to Fig. 3 there is illustrated a modification wherein, instead of the two coils l9 and 32, one coil 40 is utilized. By proper designing of the magnetic circuit, including the air gap 4| between the pole pieces 42 and 43 the pull upon the armature 44 at point 45 can be made to reach a high value sooner than the pull upon the armature 44 at the point 46 by the pole piece 42. Eventually, however, the pull at 46 will overcome the retaining force at 45 and thereupon, when the armature 44 starts moving, the air gap at 45 will increase as that at 46 decreases so that the armature will move very quickly to the closed position which represents an open position of the contacts. In this modification, the armature 44 corresponds to the armature 8 and the pole piece 42 to the core H. The armature in this modified form is preferably entirely of soft iron although magnetic inserts may be used in a non-magnetic holder, the space between the inserts constituting the necessary air gap corresponding to the gap 4|.

Referring next to Fig. 4, an additional modification is illustrated wherein the coil 50 corresponds to the coil l9 and the armature i corresponds to the armature 8. A branch magnetic circuit through pole piece 52 is provided, the armature being held at 54 until such time as the fiux across the gap 55 has increased to sufficient strength.

' As a further modification which is clear without illustration, a permanent magnet may be utilized in place of the magnetic coil 32.

Having thus described my invention,

I claim:

1. In an electro-magnetic circuit interrupter normally biased to a closed position, a main electro-magnetic means for opening the interrupter against the opposition of the biasing force, an auxiliary electro-magnetic means for resisting the opening of the interrupter, and means for simultaneously initiating excitation of both of said electro-magnetic means, said electro-magnetic means being variably related during said initial excitation in a manner such that the auxiliary electro-magnetic means is first stronger and then weaker than the main electro-magnetic means.

2. In a circuit interrupter normally biased to a closed position, a main electro-magnetic means for opening the interrupter against the opposition of thebiasing means, an auxiliary electro-magnetic means for preventing the opening of the interrupter during initial excitation of said main electro-magnetic means, and means for simultaneously initially exciting both of said electromagnetic means, said auxiliary electro-magnetic means reaching a predetermined degree of excitation more quickly than said main electromagnetic means, said main electro-magnetic means eventually reaching a degree of excitation to overcome the force of said auxiliary electromagnetic means and biasing means.

3. In a circuit interrupter normally biased to a closed position by a biasing means, a stationary contact, a movable armature, a relatively movable contact carried by said armature, supplementary biasing means urging the movable contact toward contact position, and when said movable contact in contact position, urging said armature toward contact breaking position, an operating coil operatively associated with the armature and energizable for urging the armature to contact breaking position against the force of the biasing means, and electro-rnagnetic means operatively associated with the armature and opposing the movement of the armature by the operating coil and the supplementary biasing meanstoward. contact breaking position, and capable of increasing in strength at a rate suificiently more rapid than the rate of increase of the operating coil, during initial energization of said operating coil, so that the biasing means and the electromagnetic means prevent the movement of the armature by said operating coil and said supplenicntary biasing means toward contact breaking position until the strength of the operating coil is greater than the combined strength of the main spring and the electro-magnetic means.

i. In a spring closed electro-magnetic switch, a stationary contact, a movable arnature, a relatively movable contact carried by said armature, an auxiiiary spring urging the movable contact toward contact position, and when said movable contact is in contact position, urging said armature toward contact breaking position, an operating coil operatively associated with the armature and energizable for urging the armature to contact breaking position against the force of the main spring, and electrcnnagnetic means operatively associated with the armature and opposing the movement of the armature by the operating coil toward. contact breaking position, and capable of increasing in strength at a more rapid rate than the operating coil, during initial energization of said operating coil, so that it prevents the movement of the armature by said operating coil toward contact breaking position until the strength of the operating coil is greater than the combined strength of the main spring and the electro-magnetic means.

5. In a spring closed electro-magnetic switch, a stationary contact, a movable armature, a relatively movable contact carried by said armature, an auxiliary spring operatively interposed between the said contact and the armature and urging the movable contact toward contact position and, when said movable contact is in contact position, urging said armature toward contact breaking position, an operating coil operatively associated with the armature and energizable for urging the armature to contact breaking position against the force of the main spring, and electro-magnetic means operatively associated with the armature and opposing the movement of the armature by the operating coil and the auxiliary spring toward contact breaking position, and capable of increasing in strength at a rate sufiiciently more rapid than the rate of increase of the operating coil, during initial energization of said operating coil, so that the main spring and the electro-magnetic means prevent the movement of the armature by said operating coil and said auxiliary spring toward contact breaking position until the strength of the operating coil is greater than the combined strength of the main spring .and the electro-magnetic means.

6. In a spring closed electro-magnetic switch, a stationary contact, a movable armature, a relatively movable contact carried by said armature, an auxiliary spring urging the movable contact toward contact position, and when said movable contact is in contact position, urging said armature partway toward contact breaking position, and becoming ineffective upon said partway movement of said armature toward contact breaking position against the force of the main spring and'the auxiliary spring, and electro-magnetic means operatively associated with the armature and opposing the movement of the armature by the operating coil and auxiliary spring toward contact breaking position, and capable of increasing in strength at a more rapid rate than the operating coil during initial energization of said operating coil so that the main spring and the electro-magnetic means prevent the movement of the armature by said operating coil and .said auxiliary spring toward contact breaking position until the strength of the operating coil is so great that the removal of the effect of said auxiliary spring upon slight movement of the armature is negligible relative to the strength of the operating coil.

7. In a circuit interrupter normally biased to a closed position, a main electro-magnetic means having a relatively large time constant for opening the interrupter against the opposition of the biasing force, an auxiliary electro-magnetic means having a relatively small time constant for resisting the opening of the interrupter during the initial excitation of said main electromagnetic means, and means for simultaneously initially energizing both of said electro-magnetic means, the relative values of said time constants being such that said auxiliary electro-magnetic means reaches a predetermined degree of excltation before said main electro-magnetic means, whereby said auxiliary electro-magnetic means resists the opening of the interrupter during initial excitation of said main electro-magnetic means.

8. In a normally closed circuit interrupter normally biased to a closed position, main electromagnetic means for opening the interrupter against the opposition of the biasing force, auxiliary electro-magnetic means resisting the opening of the interrupter during the initial excitation of said main electro-magnetic means, said electro-magnetic means having a variable relation to each other during initial excitation of said main electro-magnetic means, and means for de-energizing said auxiliary electro-magnetic means during opening movement of said interrupter.

9. In a spring closed electro-magnetic switch, a stationary contact, an armature, a movable contact carried by the armature, a spring for moving the armature to contact making position, an operating coil operative when energized for moving the armature in opposition to the spring to contact breaking position, auxiliary electromagnetic means energized from a source of power for augmenting the force of said spring when the contacts are closed, switch means operated by the armature when the armature moves a predetermined distance in the contact breaking direction for disconnecting the auxiliary electromagnetic means from its associated source of power.

10. In a spring closed electro-magnetic switch, a stationary contact, an armature, a movable contact carried by the armature and movable relative thereto, an operating coil operative when energized to move the armature to contact breaking position, a spring for moving the armature to contact making position and opposed to the coil when the coil is operative to move the armature to contact breaking position, an auxiliary spring concurrently urging the movable contact toward contact making position and the armature toward contact breaking position when the armature is in contact making position, and an electro-magnetic means operative to prevent the movement of the armature by the operating coil from contact making position during initial energization of the operating coil and said electromagnetic means, the magnetic force of said electro-magnetic means increasing more rapidly during its initial energization than the magnetic force of said operating coil during its initial energization.

WARD L. SMITH. 

